Political Humour, Canadian

(This joke is related to the new $2 coin that was just introduced in Canada
to replace the $2 bill)
One of the guys here at school made a joke about the future coins that
we might have:
The $5 coin. Its a ring that fits around the $2 coin. The reduction in the
amount of required metal will save the Canadian government millions.
Later, the $10 and $20 dollar rings will be gradually phased in.
It is expected that the $100 coin will also be usable as a spare tire if you
get a flat.